1. Field of the Invention
This invention relates to a matrix printer.
2. Description of the Prior Art
For example, in a wire matrix type printer which effects dot matrix printing while moving a print head in the column direction, where a dot is further to be formed, for example, between adjacent dot matrices, for the purpose of effectively utilizing printing elements limited in number, it has heretofore been the practice to cause a printed medium to be slightly deviated in the row direction to form a new dot by the same printing element or the shift the entire dot print head by a suitable amount in the row direction to form a new dot by the same printing element. It is a matter of fact that the printing speed of the present-day dot printer, even of low speed, is 100 characters/sec. or higher, and in the ordinary printing stroke, for example, where one character is formed by 5.times.7 matrices and the inter-character space is formed by an amount corresponding to one dot, the time required for the printing of the same row is 1.6 m sec. or less. For simplicity, this time of 1.6 m sec. is considered to be the least time for continuously driving one printing wire of the dot print head. That is, where printing is continuously effected by the same printing wire at the column positions other than the usual printing columns on one printing row as previously described, whether the printed medium is moved or the dot print head is moved up or down, the wire end must be brought to the next printing column position within the given 1.6 m sec. Both the printed medium and the wire print head have a considerable mass and therefore, great energy is necessary to move any one of them and accordingly, the driving device therefore becomes bulky and this actually means a great inconvenience as compared with the effect of an improved printing quality. To avoid such disadvantage, there has been devised the so-called multipass system wherein, for the formation of one character or symbol, the character-by-character formation as aforementioned (incremental printing) is not effected but only the dot column to be formed at first is effected in the first movement stroke of the print head, whereafter the printing column is shifted or the print head position is changed, and then the dot column to be formed next time, for example, the column which could not be printed in the first stroke, is effected in the second movement stroke of the print head. However, although this system is effective as a line printer, it has drawbacks in that it cannot effect incremental printing and that the printing cannot be confirmed until all the printing stroke for one line is terminated.